the extensor digitorum brevis: histological

Journal of Neurology, Neurosurgery, and Psychiatry, 1972, 35, 124-132

The extensor digitorum brevis:histological and histochemical aspects

F. G. I. JENNEKENS', B. E. TOMLINSON, AND J. N. WALTON

From the Departments of Neurology and Neuropathology, Regional Neurological Centre,General Hospital, Newcastle upon Tyne

SUMMARY Samples of the extensor digitorum brevis muscle (EDB) obtained at necropsy from 26subjects without known neuromuscular disease were examined histologically and histochemically.In the two youngest subjects, aged 2 months and 8 years, a mosaic distribution of type I and type IIfibres was present. From the second decade onwards, increasing with age, the mosaic pattern was

gradually replaced by groups of type I and type II fibres and areas of grouped fibre atrophy appeared.It is suggested that these findings may be explained by a slow process of denervation and reinnerva-tion. This process does not seem to occur to the same extent in three other distal limb muscles fromwhich specimens were also examined.

The extensor digitorum brevis muscle (EDB) is arelatively flat muscle which occupies an exposedposition on the dorsum of the foot. Largely onaccount of its isolation from other muscles andits distal position, this muscle has been usedextensively in electromyography with concentricneedle electrodes and in measurements of motornerve conduction velocity. More recently themuscle has been chosen for an electrophysio-logical method of estimating the number ofmotor units (McComas, Fawcett, Campbell, andSica, 1971). These authors discuss at some lengththe merits and also the disadvantages of thismuscle as a preparation for research purposes.

In recent investigations involving the examina-tion of various human skeletal muscles obtainedat necropsy (Jennekens, Tomlinson, and Walton,1971a, b, c) we were struck by the frequentoccurrence of appearances suggesting neuro-genic atrophy and of groups of type I and type IIfibres in the EDB's of subjects who had had nosigns or symptoms of neuromuscular disease. Aswe were unaware of any reports in the literatureon the histology and enzyme histochemistry ofthe EDB, we decided to extend our observationsto a larger number of specimens. As biopsymaterial was not available, necropsy materialwas used.Though necropsy material is not suitable for

refined enzyme histochemical investigations, it

Present address and reprint requests: Department of Neurology,University Hospital, Utrecht, The Netherlands.

124

has been shown (Susheela and Walton, 1969;Jennekens et al., 1971a, b) that type I and type IIfibres can readily be distinguished in striatedmuscles taken at necropsy within 48 hours ofdeath. This allows observations to be made onthe numbers, sizes, and shapes of the two fibretypes and on their distributions in relatively largetransverse sections of several muscles in oneindividual. In the present study the EDB wascompared with the flexor digitorum brevis (FDB),the tibialis anterior (TA), and the gastrocnemius(G) muscles.TA and EDB are innervated mainly by nerve

fibres running through the anterior root of L5and S1, the G and FDB are innervated mainly bynerve fibres from S1 and S2 spinal nerves. Theposterior tibial nerve is the peripheral nervetrunk innervating G and FDB, the TA and EDBare supplied by branches of the common peronealnerve. EDB and FDB lie at approximately thesame distance from the anterior horn cells in thespinal cord and are therefore innervated bymotor neurones with axons of approximatelyequal lengths.

METHODS

Sections of the EDB were obtained from 26 patients(Table). None of the patients had suffered beforedeath from any disease which was either long-lastingor prostrating. There was no evidence of previousneuromuscular disease in any patient and most haddied as a result of trauma or an acute illness.

Protected by copyright.

on July 21, 2022 by guest.http://jnnp.bm

j.com/

J Neurol N

eurosurg Psychiatry: first published as 10.1136/jnnp.35.1.124 on 1 F

ebruary 1972. Dow

nloaded from

http://jnnp.bmj.com/

The extensor digitorum brevis: histological and histochemical aspects

TABLEFIBRE TYPE GROUPING' IN FOUR DISTAL LIMB MUSCLES IN NECROPSY MATERIAL FROM 26 SUBJECTS

Case Age Sex Clinical data Principal necropsy fiu,dting Grade of grouping (see text)(yr)

G TA FDB EDB

I 1 M Progressive cardiac failure Congenital heart anomaly Rt 0 0 0 0Lt - - - 0

2 8 M Sudden death Head injury 0 0 0 13 11 M Sudden death Head injury 0 0 0 24 18 M Sudden death Head injury 0 0 2 25 18 M Sudden death Head injury - 0 0 26 19 F Epilepsy, sudden death Head injury - - - 27 27 M Sudden death Barbiturate overdose - - - 28 33 M Sudden death Head injury - - - 39 33 F Sudden death Head injury 0 1 1 210 35 F Sudden death Barbiturate overdose 0 - 1 311 35 F Sudden death Myocardial infarction - - - 312 42 F Sudden death Head injury - - - 313 45 M Sudden death Myocardial infarction 0 1 1 314 60 M Influenza, succumbed within 7 Bronchopneumonia I I - 3

days15 63 M Influenza, succumbed within 7 Bronchopneumonia 0 0 1 3

days16 65 F Succumbed in 6 days Mvocardial infarction - - - 317 67 M Sudden death Fractures of cervical vertebrae - - - 318 69 F Spells of dizziness, sudden death Head injury Rt 0 - 1 2

Lt I - 0 319 69 M Influenza, succumbed in 4 days Bronchopneumonia - 2 3 320 73 F Gastrointestinal haemorrhage Gastric ulcer, hiatus hernia I 0 - 221 78 M Succumbed in 4 days Myocardial infarction - - - 322 80 F Succumbed in 14 days Myocardial infarction Rt - - - 2

Lt - - - 323 80 F Sudden death Cerebral haemorrhage 1 2 2 324 84 M Congestive cardiac failure, Myocardial fibrosis - - - 3

bronchitis25 85 M Right hemiplegia, sudden death Cardiac tamponade Rt - - - 3

Lt - - - 326 88 F Giddiness, confusion, sudden Myocardial infarction - - - 3

death

-: not analysed. 0: no grouping.

In cases 1, 18, 22, and 25 specimens were takenfrom both sides of the body; in all other casesmaterial was collected from one side only. In 14 ofthe 26 patients specimens were also taken from theG, TA, and FDB.A part of each specimen was frozen in hexane

which had been cooled either in liquid nitrogen or ina slush of ice of carbon dioxide and alcohol. Trans-verse sections of 10 Xu thickness and up to 2-5 cm2were cut in a cryostat at a temperature of - 20°C.The activity of myofibrillar ATP-ase and of di-phosphopyridine nucleotide diaphorase (NADHdiaphorase) was determined according to themethods of Padykula and Herman (1955) and ofScarpelli, Hess, and Pearse (1958) respectively.Other transverse sections were stained with haema-toxylin and eosin. Material which had been fixed in1000 formalin and which had been embedded inparaplast was sectioned transversely as well as

longitudinally and stained with haematoxylin andeosin and phosphotungstic acid haematoxylin.

In this material a gradual transition with increas-ing age was observed from a pure mosaic pattern onthe one hand to complete grouping with large groupsin a transverse section of the whole muscle on theother hand. To facilitate comparison, the extent of

grouping was assessed semiquantitatively. If a trans-verse section was composed largely of a mosaicpattern with groups of at least 60 fibres in smallparts of the section, grouping was classified as beinggrade 1. Grouping was classified as grade 2 if itoccurred in about 500,, of the whole section and asgrade 3 if groups occupied the whole or nearly thewhole of the transverse section.

RESULTS

The volume of the four limb muscles examinedwas often somewhat less in old age than inyouth. This decrease was particularly striking inthe EDB. In young people the belly of thismuscle causes the skin of the lateral half of thedorsum of the foot to bulge upwards slightlyabove the forepart of the calcaneus and abovethe cuboid bone. At necropsy this muscleappeared atrophic in patients between 60 and 90years of age when compared with its appearancein subjects younger than 20 years. The EDB ofseven of the 16 specimens examined from patientsbetween 60 and 90 years old had largely been re-placed by connective tissue and fat.

125P

rotected by copyright. on July 21, 2022 by guest.

http://jnnp.bmj.com

/J N

eurol Neurosurg P

sychiatry: first published as 10.1136/jnnp.35.1.124 on 1 February 1972. D

ownloaded from


F. G. L Jennekens, B. E. Tomlinson, and J. N. Walton

FIG. 1. Transverse cryostatsection from the EDB of ababy of 2 months. MyosinATP-ase, x 120. Distributionof type I and type II fibres in amosaic pattern.

HISTOLOGY AND HISTOCHEMISTRY OF EDB Therewas a fine mosaic pattern in the transverse sec-tions of this muscle in a baby of 2 months (Fig.1) and in a boy of 8 years. In this latter case agroup of about 100 type I fibres was seen at oneside of the section, corresponding to the inner-most part of the muscle. This innermost partshowed a slight preponderance of type I fibres;in the outer, more dorsal part there was a slightpreponderance of type II fibres.The EDB of case 3, a boy of 11 years, presented

an entirely different picture. Small groups of 30to 80 histochemically uniform fibres (Fig. 2) werescattered all over the sections, leaving a mosaicpattern in less than 500 of the transverse sec-

tions. Though groups of type I fibres occurredslightly more frequently, groups of type II fibreswere present as well. There was no obvious in-crease in the variation of fibre size, either indifferent groups or in different fields of thesections.With minor variations, the same picture as that

seen in case 3 appeared to be present in the EDB'sof all other cases up to the age of 30 years (cases4, 5, 6, and 7). Amid the mosaic pattern groupsof both fibre types were spread all over the sec-tions. In case 4 a group of 20 to 30 atrophic fibreswas lying at the extreme edge of the cryostatsection. We were not sure how to interpret thisfinding. In case 7 the variation in fibre size was* :-. X . 'g5ifi > ' 89't ' ' O' i Y X . . TY :O.:gi -s:: ......... 've. .X ......... °.: : | n , .................. : . 3,<? .4 - ' ................. .. :::: t . Lt ! i i .w | t :;9 '.° ^ w.

ii | g t. Ss S. .S ..s N .. t^S ' |.^ .Po 3 .XaN v w a f.. f s ... . . .

w...X_F

FIG. 2. Transverse cryostatsection from the EDB ofa boyof 11 years. Myosin ATP-ase,x 120. Small groups of type Iand type II fibres.

126

*11.

xr...*;

.Alib



j.com/

J Neurol N


ebruary 1972. Dow

nloaded from



FIG. 3. Transverse cryostatsection from the EDB of aman of 27 years. Myosin ATP-ase, x 120. Atrophic andelongated fibres between othersof normal size.

thought to be beyond the normal range. Isolated,atrophic, angulated fibres (Fig. 3) were seen

among others of normal size.In patients between 30 and 50 years of age,

groups generally tended to be of a larger sizethan in patients below the age of 30 (Fig. 4).Some evidence of a mosaic pattern remained inthe EDB of case 9, but groups only were seen incases 8, 10, 11, 12, and 13. The variation in fibresize was within the normal range in three speci-mens, but abnormal in three others. In case 13fibres within groups were often surprisinglyuniform in size, but there was an abnormalvariation in fibre size between different groups.A small bundle of atrophic fibres of type Iwas seen in case 10 (Fig. 5) and many bundles of

atrophic fibres occurred in case 11 (Fig. 6); thecharacteristic appearances of neurogenic atrophywere thus present in both of these cases.

It was not so much the extent of type groupingas the frequency of grouped fibre atrophy whichmarked the difference between patients of 30 to50 years and those of 60 to 90 years. Only threeof 13 patients in the 60 to 90 year categoryshowed a recognizable mosaic-like pattern insome small parts of the EDB; in all other patientsin this age group the sections of the EDB werecompletely occupied by groups which were oftenlarge. Groups of type I fibres were slightly morefrequent than groups of type II fibres. Groups ofintermediate fibres were seen frequently insections stained for NADH diaphorase activity.

FIG. 4. Transverse cryostatsection from the EDB of aman of45 years. DPNHdiaphorase, x 50. Fibre typegrouping, the mosaic pattern isalmost completely absent.

127P


http://jnnp.bmj.com

/J N

eurol Neurosurg P


ownloaded from



FIG. 5. Transverse cryostatsection from the EDB of awoman of35 years. MyosinATP-ase, x 120. Grouping oftype I and type IH fibres and agroup of atrophic type I fibres.

In case 17, all of the fibres which were notatrophic were histochemically uniform.

Evidence suggesting denervation atrophy waspresent in the EDB of 11 out of 13 elderly (60 to90 years) patients. In four specimens only a fewfascicles were not atrophic. Type I, intermediate,and type II fibres in three of these specimenswere large or hypertrophic, the shortest diam-eters (Jennekens et al., 1971a) of the largestfibres being 100 V. in case 17, 130 ,u in the leftEDB of case 25, and 180 pi in case 21 (Fig. 7).These large fibres had acquired a rounded shapeand some contained internal nuclei (Fig. 8).Occasional fibres in specimens of this age groupshowed a target-like appearance, irregulardistribution of oxidative enzyme activity in type

i7:., ,

< . , z., !.,;Z-1

4.K'

I fibres and fibre necrosis. It is, of course, possiblethat such irregularity of oxidative enzyme ac-tivity could be due to postmortem autolysis(Jennekens et a!., 1971c).

HISTOLOGY AND HISTOCHEMISTRY IN THE FDB, TAAND G Material was removed from these threemuscles in eight subjects varying in age from 2months to 45 years. Histological examinationdid not reveal any obvious pathological changes.Grouping of type I and of type II fibres occurredin four of eight specimens of the FDB and wasclassified as either grade 1 or grade 2. Groupingwas infrequent in the TA and G and was nevergreater than grade 1.

Grouping and signs of neurogenic atrophy

FIG. 6. Transverse cryostatsecionfrom the EDB of a

woa (f35 years. MyosinATP-ase, x 120. Fibre type

atrophic fibres; some inter-

Ws j~Y mediate fibres are present.

.,-;,-- '!

128

KI



j.com/

J Neurol N


ebruary 1972. Dow

nloaded from



FIG. 7. Transverse cryostatsection from the EDB of aman of 78 years. DPNHdiaphorase, x 120. Fibrehypertrophy, irregulardistribution of oxidativeenzyme activity in some fibres.

ltv-- t:fRo ~=-.

Vt. 9f. * -

were, however, seen regularly in specimens of thesame muscles obtained from patients between 60and 90 years of age. The FDB was completelygrouped in one case; in all other specimens themosaic pattern was preserved, at least partly. InFDB and G both groups of type I and of type IIfibres were present; in the TA grouped fieldswere usually composed of type I fibres; occasion-ally, however, small groups of type II fibresoccurred. Grouped fibre atrophy was seen inthree of six specimens of the FDB. Even whenevidence of neurogenic atrophy was widespread,many fascicles were spared. Fibre hypertrophywas not observed. Signs of neurogenic atrophywere seen in four specimens of the G and in onespecimen of the TA.

Grouping could not be graded in the G of case19, due to extensive necrobiotic changes whichwere probably caused by ischaemia; the TA,FDB, and EDB of this patient were not similarlyaffected. Fibres with a target-like or targetoid-like appearance were seen in several specimens(Fig. 9). Irregular distribution of oxidativeenzyme activity in type I fibres, fibre necrosis,and phagocytosis were also observed in occas-ional fibres of several specimens (Jennekens etal, 1971c).

Statistical analysis of the extent to whichgrouping occurred showed that the four limbmuscles examined were not identical in thisrespect (Friedman's test, P<001). There wassignificantly more grouping in the EDB than in

_ 4 ..* !, }).K * : . vvr E^

a

N

*f >.

*ts b< a i8z ;X e +o~I?p +-<'tJ'

Ca s

%.. a',L'.

C.. . 4.

f

u-SE

'a. --*cC

.t p

I,J

FIG. 8. Transverse cryostatsection from the EDB of aman of 67 years. Haema-toxylin and eosin, x 120.Groups of atrophic fibres.Rounded appearance of somefibres and fibres with internalnuclei.

129P


http://jnnp.bmj.com

/J N

eurol Neurosurg P


ownloaded from



Ci

-7.'k~~~~~~~~~~~~ .

FIG. 9. Serial transverse sections from the gastrocnemius muscle of a woman of 80 years(case 23) x 480. A target-like fibre. (a) DPNH diaphorase, a zone of low enzyme activity in atype I muscle fibre; (b) myosin ATP-ase, there is a zone of low enzyme activity surrounded bya ring of slightly higher activity in the same fibre (c) haematoxylin and eosin, at the site oflow enzyme activity there is a purple core. Another muscle fibre (bottom left) shows a smallzone of similar characteristics.

the FDB (Wilcoxon's matched-pairs signed rankstest, P < 0 01), in the TA (ditto, P < 0-01), and inthe G (ditto, P < 0 01). The figures suggested thatgrouping occurred non-significantly more oftenand more extensively in the FDB than in the TAand in the G. No difference could be shownbetween the TA and the G.

DISCUSSION

Recently it has been said that muscle fibres ofone motor unit are intermingled, within aterritory of some millimetres, with fibres of othermotor units (Ekstedt, 1964; Edstrom andKugelberg, 1968; Mayer and Doyle, 1969). Thisfinding is pertinent to the interpretation of thephenomenon of grouped fibre atrophy in neuro-genic diseases. Interruption of a motor axonresults in denervation of a number of isolatedmuscle fibres. It is now known that these fibresmay be reinnervated by sprouts of nearby motoraxons of other motor units. Volumetric changesin denervated muscle fibres may be preventedwhen sprouting occurs rapidly (Hildebrand,Joffroy, and Coers, 1968). Enlargement of motorunits by collateral ramification and reinnervationincreases the likelihood that muscle fibres of oneunit will be grouped into sub-units. Assuming

that the muscle fibres of a motor unit are histo-chemically uniform (Edstrom and Kugelberg,1968; Mayer and Doyle, 1969), reinnervationthen results in grouping of fibres of one type. Itis likely, too, that following recent reinnervation,muscle fibres may show an intermediate intensityof enzyme staining while in the process ofchanging from one fibre type into another; thusa finding of many intermediate fibres could sug-gest recent reinnervation. The degree of fibretype grouping is probably related to the amountof collateral ramification (Karpati and Engel,1968). Subsequent denervation of such pre-viously enlarged motor units will then lead togrouped fibre atrophy which will probably beeven more striking if axonal sprouting has beeninadequate. Muscle fibre atrophy in neurogenicdisease is the result of denervation combinedwith insufficient reinnervation (Coers, 1969).

In the EDB fibre type grouping occurredstrikingly often, sometimes in young adults. Webelieve that this grouping is probably caused bya process of denervation and reinnervation. Agrouped pattern was not apparently present inearly infancy, but it subsequently developedgradually, as was shown by the mosaic patternin the two youngest children and by the changefrom small groups with some residual evidence

130P


http://jnnp.bmj.com

/J N

eurol Neurosurg P


ownloaded from



of a mosaic pattern in the age range between 10to 30 years, to large groups in older individuals.An alternative explanation would be to suggestthat in man, as occurs in some muscles of thelower mammals, other causes for grouping oftype I and type II fibres than denervation andsubsequent reinnervation are conceivable. How-ever, the concept of a continuing process ofpartial denervation and reinnervation occurringin adult life seems to us more likely. Thus wefound few if any groups of atrophic fibres of uni-form histochemical type in children and youngadults. On the other hand, in middle age and inelderly subjects groups of atrophic fibres of onehistochemical type, showing the characteristicsof neurogenic atrophy, were seen with increasingfrequency; this finding suggested that there hadprobably been a previous redistribution of fibresof one motor unit into sub-units.

Effective sprouting depends on the survival ofan adequate number of motor axons. When thenumber of motor axons which are available forcollateral reinnervation has decreased, the chanceincreases that the distance between a denervatedmuscle fibre-or a group of denervated musclefibres-and the nearest axon will not be bridged(Weiss and Edds, 1946). This explains the in-crease in grouped fibre atrophy in older patients.In the EDB's of some of the oldest patients even' myopathic' changes and fibre hypertrophyoccurred, exactly as may be seen in motorneurone disease and in chronic neuropathies.There was less grouping and denervation in

the three other limb muscles. If more materialhad been examined it might have been possibleto demonstrate a difference between the FDB andthe TA and G, but even in the FDB groupingoccurred significantly less often than in the EDB.There is no evidence to indicate a particular

liability of the nerves which innervate the EDBto traumatic lesions. The position of these nervefibres in the common peroneal nerve is not par-ticularly exposed (Sunderland, 1968). It is, how-ever, known that the anterior tibial nerve showssubstantial variation in fibre density (Gairns,Garven, and Smith, 1960; Swallow, 1966) and adecrease of fibre density with increasing age.Gairns et al. (1960) suggested badly fitting shoesas a possible cause for the occurrence of lowfibre densities in the digital nerves of young sub-jects. The motor nerves of the EDB at theirentrance into this muscle might also be com-pressed intermittently by shoes. This hypothesiswould be supported if non-shoe-wearing indi-

viduals were found to retain a mosaic pattern offibre types into late life. Further, we were oftensurprised at postmortem examination to findhow firmly the EDB was compressed by thetautly stretched tendons of the extensor digi-torum longus muscle on their way to the digits.Entrapment caused by one or both of thesefactors might explain the occurrence of changessuggesting denervation at a relatively early age,the exceptional regularity with which type groupsof muscle fibres occur, and the slowness of theprocess of denervation and reinnervation in theEDB.

Our thanks are due to Dr. A. J. McComas for hisstimulating interest and helpful suggestions, to Mr.J. C. van Houwelingen for the statistical analyses, toMiss D. Kitchener and Mr. M. Stone for thetechnical work, and to Mr. A. Piso for micro-photography. At the time this work was carried outone of us (F.G.I.J.) was the holder of a fellowship ofthe Netherlands Organization for the Advancementof Pure Research. The work was aided by grantsfrom the Muscular Dystrophy Associations ofAmerica, Inc., the Medical Research Council, andthe Muscular Dystrophy Group of Great Britain.

REFERENCES

Arnold, N., and Harriman, D. G. F. (1970). The incidence ofabnormality in control human peripheral nerves studied bysingle axon dissection. Journal ofNeurology, Neurosurgery,and Psychiatry, 33, 55-61.

Coers, C. (1969). Morphological changes in motor units inhuman and experimental neuropathies. InternationalCongress Series Excerpta Medica, 199, 365-376.

Edstrom, L., and Kugelberg, E. (1968). Histochemical com-position, distribution of fibres and fatiguability of singlemotor units. Anterior tibial muscle of the rat. Journal ofNeurology, Neurosurgery, and Psychiatry, 31, 424-433.

Ekstedt, J. (1964). Human single muscle fiber action poten-tials. Acta physiologica Scandinavica, 61, Suppl. 226, 1-96.

Gaims, F. W., Garven, H. S. D., and Smith, G. (1960). Thedigital nerves and the nerve endings in progressive oblitera-tive vascular disease of the leg. Scottish Medical Journal, 5,382-391.

Harriman, D. G. F., Taverner, D., and Woolf, A. L. (1970).Ekbom's syndrome and burning paraesthesiae. A biopsystudy by vital staining and electron microscopy of theintramuscular innervation with a note on age changes inmotor nerve endings in distal muscles. Brain, 93, 393-406.

Hildebrand, J., Joffroy, A., and Coers, C. (1968). Myoneuralchanges in experimental isoniazid neuropathy. Electro-physiological and histological study. Archives ofNeurology,19, 60-70.

Jennekens, F. G. I., Tomlinson, B. E., and Walton, J. N.(1971a). The sizes of the two main histochemical fibretypes in five limb muscles in man: an autopsy study.Journal of the Neurological Sciences, 13, 281-292.

Jennekens, F. G. I., Tomlinson, B. E., and Walton, J. N.(1971b). Data on the distribution of fibre types in fivehuman limb muscles: an autopsy study. Journal of theNeurological Sciences, 14, 245-257.

131P


http://jnnp.bmj.com

/J N

eurol Neurosurg P


ownloaded from


F. G. L. Jennekens, B. E. Tomlinson, and J. N. Walton

Jennekens, F. G. I., Tomlinson, B. E., and Walton, J. N.(1971c). Histochemical aspects of five limb muscles in oldage: an autopsy study. Joutrnal ofthe Neurological Sciences,14, 259-276.

Karpati, G., and Engel, W. K. (1968). 'Type grouping'in skeletal muscles after experimental reinnervation.Neutrology (Minneap.), 18, 447-455.

Lascelles, R. G., and Thomas, P. K. (1966). Changes due toage in internodal length in the sural nerve in man. Journalof Neurology, Neutrosurgery, and Psychiatry, 29, 40-44.

McComas, A. J., Fawcett, P. R. W., Campbell, M. J., andSica, R. E. P. (1971). Electrophysiological estimation ofthe number of motor units within a human muscle. Journalof Neuirology, Neurosurgery, and Psychiatry, 34, 121-131.

Mayer, R. F., and Doyle, A. M. (1969). Studies of the motorunit in the cat. Histochemistry and topology of anteriortibial and extensor digitorum longus muscles. InternationalCongress Series Excerpta Medica, 199, 159-163.

O'Sullivan, D. J., and Swallow, M. (1968). The fibre size andcontent of the radial and sural nerves. Joutrnal ofNeurology,Neuirosurgery, and Psychiatry, 31, 464-470.

Padykula, H. A., and Herman, E. (1955). The specificity ofthe histochemical method for adenosine triphosphatase.Journal of Histochemistry and Cytochemistry, 3, 170-195.

Scarpelli, D. G., Hess, R., and Pearse, A. G. E. (1958). Thecytochemical localization of oxidative enzymes. 1. Di-phosphopyridine nucleotide diaphorase and triphospho-pyridine nucleotide diaphorase. Joutrnal of Biophysical andBiochemical Cytology, 4, 747-752.

Sunderland, S. (1 968). Nerves and Nerve Injliries. Livingstone:Edinburgh.

Susheela, A. K., and Walton, J. N. (1969). Note on thedistribution of histochemical fibre types in some normalhuman muscles. A study on autopsy material. Joutrnal ojthe Neurological Sciences, 8, 201-207.

Swallow, M. (1966). Fibre size and content of the anteriortibial nerve of the foot. Journal ofNeurology, Neutroslurgery,and Psychiatry, 29, 205-213.

Weiss, P., and Edds, M. V. J. (1946). Spontaneous recoveryof muscle following partial denervation. American Journalof Physiology, 145, 587-607.

Woolf, A. L. (1966). The pathology of the intramuscularnerve endings. International Congress Series, ExcerptaMedica, 100, 641-647.

132P


http://jnnp.bmj.com

/J N

eurol Neurosurg P


ownloaded from


the extensor digitorum brevis: histological

Documents